Where the Ice Ends: Calving and Ice-Ocean Interactions at Helheim Glacier and Beyond

Continued mass loss of the Greenland Ice Sheet has contributed to sea level rise at a rate of 0.8 mm year^-1 since 2002, with ice dynamics accounting for $66 \pm 8$\% of the mass loss signal. One of the main components of this dynamic mass loss signal is iceberg calving, the detachment of ice into the ocean. Ice dynamic and ice-ocean processes that influence iceberg calving occur across a range of spatial (cm to km) and temporal (minutes to years) scales, making them difficult to capture with existing observational strategies. To quantify these processes, we installed two autonomous terrestrial laser scanners (ATLAS) overlooking the terminus at Helheim Glacier, East Greenland, the first in 2015 and the second in 2018. Each laser scanner system scans every 6 hours during non-winter months and once a day during winter. Together, these systems generate an extraordinary amount of data, which we use to create georeferenced point clouds, digital elevation models, velocity, and strain rates of Helheim Glacier's terminus region. \par This research applies new methods for computationally efficient displacement calculations for glacier surfaces to uncover the dominant calving mechanisms at Helheim Glacier. We find that surface depressions appear at a consistent spot near a subglacial ridge upflow from Helheim Glacier's terminus. The subsequent calving events from these surface depressions and non-surface-depression calving events did not have a sustained increase in velocity. Furthermore, Helheim glacier's consistent calving style also leaves similar iceberg configurations within its sikkusak (ice mélange). This led to questions regarding how much heat is used to melt large icebergs from incoming Atlantic waters before that heat reaches the terminus. This process formed the basis for chapter 4 of this dissertation. Combining an image segmentation model with SpatioTemporal Asset Catalogs, we generate iceberg distributions from four fjord systems and input these distributions into an iceberg melt rate model. We find that iceberg melt can use $\sim$ 10 \% of heat from Atlantic water, but that number can be as high as 40 \% depending on the turbulent heat and salt transfer coefficients used.

Grantor dc:publisher

University of Kansas

Year dc:date.issued

2024

Author dc:creator

• Shahin, Michael

Advisors dc:contributor.advisor

• Van der Veen, Cornelis J.
• Stearns, Leigh A.

• Geophysics
• Geographic information science and geodesy
• Environmental science
• Helheim Glacier
• Ice Dynamics
• Iceberg Calving
• Icebergs
• Terrestrial Laser Scanners

Language dc:language.iso

en

Dc Identifier Other

http://dissertations.umi.com/ku:19870

OAI identifier oai:identifier

oai:kuscholarworks.ku.edu:1808/38427